The majority of beers are made using exactly 4 ingredients: malted barley, hops, yeast, and water. Although other grains are sometimes used (e.g., wheat, oats, rice) and additional ingredients can be added to impart incremental flavours (fruits, herbs, spices, etc.) most flavour, colour, and mouthfeel differences come from these 4 ingredients alone.
A cereal grain with a husk, similar to wheat or rye. The grains are malted (i.e., soaked to trigger germination) before use in brewing to awaken the enzymes used to convert the starches to sugars. The malted barley is then dried and kilned.
Barley is the main source of sugar and nutrients for yeast. It imparts body, flavour (from bready to coffee-like), and colour (from very pale to very dark) to the beer.
A small pinecone-shaped flower grown on a bine, most commonly grown in Europe, Canada, USA, and New Zealand. After harvest, hops are dried and usually pressed into a pellet. Hops impart bitterness, flavour, and aroma to beer, and they are highly antioxidant and antibacterial. Flavours can be herbal, floral, citrus, and fruity.
Yeast is a living microscopic organism. There are two major classes of yeast: ale (top-fermented, at higher temperatures) and lager (bottom-fermented at cooler temperatures for longer). Ale yeast imparts a more fruity and estery beer, whereas lager yeast imparts a cleaner, crisper, and drier beer. Yeast convert sugars to ethanol and carbon dioxide, giving us two of our favourite components of beer. Although most yeast is added by brewers during the brewing process, it is also possible to spontaneously ferment beer without the use of pure cultured yeast. Instead the wort is left to cool down in the night air where natural and wild yeasts fall into it, creating sour and funky flavours.
Water used in brewing must be clean and potable, free of chlorine and other chemicals. It accounts for up to 94% of the beer and also imparts flavour and pH to the beer.